Laser heat treating, also known as laser hardening, is a surface modification process used to increase wear resistance or extend the lifetime for items ranging from household tools to parts in automobile manufacturing and tooling in heavy industry and transport sectors. Laser hardening is most commonly used for steel and cast iron materials. Lasers transform target areas on metal parts by controlled localized heating while preserving the metallurgical properties of the base material.

Absorption depends on the material type, carbon content, microstructure, surface condition, size and geometry and is typically restricted to surface layer. The depth of hardening ranges from 0.2–2.0 mm. The heated area can be controlled with beam shaping optics. As a result, laser heat treating provides manufacturers a precise and controlled process to modify their tooling and equipment for increased wear resistance.

Cross-section of a laser hardened camshaft

Laser Hardening with 6 kW IPG fiber laser, courtesy of Preco

Typical process speeds range from 10 to 150 cm per minute. Depth of hardening will decrease as speed increases. Achievable depth will depend on the make up of alloy. Typical width of pass values achievable with readily available equipment range from 0.5 mm to 5 cm. Smaller or larger values are possible with specialized setups.

The choice of a mode of laser operation for surface hardening mainly depends on the part itself. Most hardening applications require CW beams, such as in track hardening of most industrial tools. Some intricate parts require pulsed lasers such as IPG's YLPN Mega Pulse ytterbium pulsed laser.

Most near IR lasers can be used for hardening applications, as the main parameter required to harden the material to desired depth and hardness is the laser power. Iron based materials readily absorb 1 micron wavelength eliminating the need for pre-applying absorptive coatings to parts in the case of CO2 lasers.